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Converting CX bike to 36T cassette?

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Converting CX bike to 36T cassette?

Old 05-16-22, 12:27 PM
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humancannonball
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Converting CX bike to 36T cassette?

Hello everyone,

I have been searching for info online all morning, and am having trouble finding a straight answer (but... when is there ever a straight answer?). Sorry if this has been covered before, but if it has, I couldn't find it.


I'm going to be riding the Iron Horse Bicycle Classic here in Colorado at the end of the month (the new Ouray to Silverton Red Mountain Pass tour). The trip to the top of the pass is 12.5 miles, and just about 3300ft. of elevation gain. I just bought an older used Ibis Hakkalugi (2009ish manufacture date) , and it currently has a Sram Force 50-34T double in the front and a Sram 12-27T cassette in the rear. I'm planning on using the bike as my road and light gravel bike. However, I'm having a bit of a panic because I have a creaky knee which tends to give me trouble on sustained climbs. My legs aren't the problem, it's my knee. So I'd like to spin up the mountain passes and save my knee, so I would like to achieve close to a 1:1 ratio between my inner chainring and my largest cassette cog. So I'd like to either fit a cassette with either 34T or a 36T large cog on the bike to give me the best chance of finishing the ride without blowing out my knee.

At the moment I have a SRAM Force rear mech (but can't figure out if it's short or medium cage). What I have gleaned from my research is that I'll likely be needing to buy a new rear (MTB?) derailleur in order to fit the new 34T or 36T cassette on the bike.

I'd like to retain the old Force drop bar shifters, so whatever solution I find would ideally be compatible with these.

Anyone with straightforward ideas how this might be achieved?

(By the way, I tried attaching photos of my rear mech, and for whatever reason, I get a message saying that I can't include any URLs until I've posted at least 10 messages... but I'm not including any URLs? I'm just attaching JPEGs, so I don't know what the deal is. In any case, my rear derailleur has this stamped on the back of it: 27T20072659.)

Thanks!
Eric
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Old 05-16-22, 10:00 PM
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No replies yet. But I did hear that a SRAM Force 1 11 speed medium cage derailleur will work with a 10 speed cassette up to 36T. Does anyone know if this is actually the case?

Thanks.
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Old 05-17-22, 12:32 AM
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Originally Posted by humancannonball
No replies yet. But I did hear that a SRAM Force 1 11 speed medium cage derailleur will work with a 10 speed cassette up to 36T. Does anyone know if this is actually the case?
SRAM 10-speed and 11-speed road rear derailleurs use the same actuation ratio, so it's a Force 1 11-speed rear derailleur would work with your shifters. The medium-cage version is designed to deal with 36-tooth cogs, so you're fine there as well.

However.

Force 1 derailleurs do not have a geometry that's intended to work well with front shifting, nor do they have high chain wrap for tolerating a wide-range multi-ring setup. You might be able to "make it work" to some extent, but it won't be optimal. If you're thinking about getting a new rear derailleur to make your planned setup work, a 2x10 GX would probably be more appropriate.
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Old 05-17-22, 05:55 AM
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There are companies that make longer cage adapters that could possibly extend the range. I have shimano, and use a 34. It is outside of their ideal range, but just adjusting the b screw was all I needed to do (to get the cage above the big cog). In my case 36 would probably be pushing it too far. What is the stated range for your derailleur?
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Old 05-17-22, 10:13 AM
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If you have 10 speed SRAM Road you can use 10 speed SRAM Mountain derailleurs since they utilize the same "Exact actuation" cable pull (not to be confused with 11 speed "x actuation")
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Old 05-18-22, 09:19 AM
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Thanks everyone for the valuable input.

So what I ended up doing is ordering a SRAM x7 long cage derailleur and a 12-36T cassette off of eBay.

Hopefully it'll all work!

Thanks again.
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Old 05-21-22, 03:56 PM
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So, I've mounted the 11-36T cassette on my wheel, and the SRAM X7 MTB long cage rear derailleur on the frame, adjusted everything, and it seems to work fine. I'm getting a lot of chain rub on the front derailleur when I'm in my smallest front chainring / largest cog, so will look into that to sort it out, but otherwise it's a success. Now let's hope what I've done is enough to prevent my knee from failing during the race.

Thanks everyone for your input, I really appreciate it.
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Old 05-25-22, 10:59 AM
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I ran a SRAM red 10pm shifter with a x7 der for a season. 2x setup with 34/46 and 34t cassette. It worked fine but the 1x1 ratio was tough slogging for me on long, steep climbs.

With the climb you are looking at, I wonder if you will be able to maintain a decent enough pace to spin? That is a brutal ascent. Since I’m not exactly Lachlan Morton, I would consider a 2x mountain crankset for that. They can be bought used for decent prices.
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